Processes for fabricating printed wiring boards using dendritic polymer copper nanocomposite coatings

ABSTRACT

An inexpensive process for depositing an electrically conductive material on selected surfaces of a dielectric substrate may be advantageously employed in the manufacture of printed wiring boards having high quality, high density, fine-line circuitry, thereby allowing miniaturization of electronic components and/or increased interconnect capacity. The process may also be used for providing conductive pathways between opposite sides of a dielectric substrate and in decorative metallization applications. The process includes steps of depositing a radially-layered dendritic copolymer on selected surfaces of a dielectric substrate; cross-linking the radially-layered dendritic copolymer to form a dendritic polymer network; sorbing metal cations into the cross-linked dendritic polymer network; reducing the metal cations to form a nanocomposite composition exhibiting adequate surface electrical conductivity for electroplating; and electroplating a metal onto the nanocomposite composition to form an electrically conductive deposit.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] The U.S. Government may have certain rights in this inventionwhich was made under U.S. Army, Space and Missile Defense Commandgovernment contract No. DASG60-00-M-0128.

FIELD OF THE INVENTION

[0002] This invention relates to processes for depositing anelectrically conductive material on a selected surface of a dielectricsubstrate, and in particular embodiments of the invention to processesfor forming electrically conductive vias in multi-layer printed wiringboards and processes for forming electrically conductive circuitpatterns on dielectric substrates.

BACKGROUND OF THE INVENTION

[0003] Competition in the electronics industry is currently being drivenby a continual need for smaller components and devices. Miniaturizationwill likely remain a fundamental driving force for the electronicsindustry for the foreseeable future. In order to meet the requirementfor continually smaller electronic components on packages such asprinted wiring boards and laminated chip carriers, it will be necessaryto develop printed circuit fabrication techniques which allow narrowercircuit patterns and higher resolution.

[0004] Typically, manufacturers employ three technologies forfabrication of printed wiring boards. These include the many varietiesof subtractive, semi-additive, and full additive processes forfabricating fine-line circuitry on printed wiring boards. Each of theseprocesses has known difficulties and limitations with regard toproducing high quality, high density, fine-line circuitry.

[0005] A conventional subtractive process requires that a full panelplating of copper be employed followed by imaging and developing of anovercoated resist layer, followed by etching of the copper in areaswhere the resist was removed. Major problems associated with thisprocess include the fact that large amounts of copper must be etchedaway and that it is common for undercutting of the remaining circuitryto occur, especially the well known galvanic etching in areas wherenoble metals are present in proximity to the copper circuitry. There isalso a problem of insufficient resolution using the subtractive process.This significantly limits the ultimate density of the fine-linecircuitry. For example, it is well known that as the line or spacedimension approaches the thickness of the layer to be etched,subtractive etching becomes unacceptable. To remedy this situation, theetch mask must be made larger than the desired feature to allow for thislateral etching.

[0006] To circumvent problems associated with the subtractive process,additive processes have been employed. However, problems are encounteredwith the need for an adhesion promoting seed layer that must be appliedafter a photoresist layer is imaged. This seed layer covers not only thedesired areas to be plated but also covers the top surfaces of thephotoresist layer. This can cause copper to be plated in areas wherecopper plating is not desired. To circumvent this problem, thephotoresist must be chemically or mechanically cleaned of the seedlayer. Mechanical etching of the seed layer is known to cause physicaldefects in the final product due to minute particles causing conductivejunctions between what should have been discrete circuit lines. Anotherpotential defect caused by mechanical cleaning is that stress placed onthe microcomponent can potentially cause delamination. Also, the processis relatively expensive due to the required build-up of coppermicrocircuitry during electroless plating.

[0007] To address problems associated with both the additive andsubtractive processes, a semi-additive process has been utilized. Atypical semi-additive process involves laminating a thin layer of copperto a substrate, coating the thin layer of copper with a resist layer,imaging and developing the resist layer to expose selected portions ofthe underlying thin copper layer, electroplating the exposed areas ofthe thin copper layer, removing the remaining photoresist, and etchingthe uncovered thin copper layer to create discrete microcomponentfeatures. The minimum thickness of the copper foil that can be appliedin the semi-additive process is limited by handling problems during thelamination process, and this minimum thickness is larger than would bedesired in order to create extremely fine line features.

[0008] In order to provide electrical continuity between opposite sidesof a substrate having printed circuitry on both sides, metallizedthrough-holes or vias are provided in printed wiring boards. Thepredominant method for metallization of through-holes or vias is byelectroless copper plating followed by electroplating. This process usesas many as 8 separate steps involving as many as 17 processing tanks.The process uses chelated copper cations in solution and formaldehyde asa reducing agent. The formaldehyde is toxic and is being legislated outof use, while the waste treatment and recovery of chelated co percations is particularly difficult. Further, adhesion of electrolesscopper to a glass/epoxy core of FR-4 laminates is a challenging problem,especially under increasingly stringent thermal cycling testing. Thereare alternative electroless plating processes on the market, but theseprocesses cannot meet the testing requirement for adhesion in thermalcycling in flex-rigid boards for certain military and otherapplications.

[0009] Accordingly, there is a need for improved processes forselectively depositing an electrically conductive material on adielectric substrate. In particular, an additive process for fabricatingfine-line circuitry on printed wiring boards which overcomes theproblems associated with conventional additive, subtractive andsemi-additive processes would be desirable. Further, improved processesfor metallization of the walls of through-holes or vias in printedwiring boards, which eliminate problems associated with electrolessplating, would be highly desirable.

SUMMARY OF THE INVENTION

[0010] The invention provides a relatively inexpensive process fordepositing an electrically conductive material on a selected surface ofa dielectric substrate. The process may be advantageously employed inthe manufacture of printed wiring boards having high quality, highdensity, fine-line circuitry, whereby further miniaturization ofelectronic components and/or increased interconnect capacity may beachieved. The processes of is invention may also be advantageouslyemployed as an alternative to electroless plating in a variety ofapplications, including metallization of through-holes used forproviding conductive pathways between opposite sides of a dielectricsubstrate.

[0011] The process includes the following steps: (a) depositing on aselected surface of a dielectric substrate a radially-layered dendriticcopolymer having a hydrophilic interior and an organosilicon exterior;(b) cross-linking the radially-layered dendritic copolymer to form adendritic polymer network having hydrophilic and hydrophobic nanoscopicdomains; (c) sorbing metal cations in the cross-linked dendritic polymernetwork; (d) reducing the metal cations in the cross-linked dendriticpolymer network to form a nanocomposite composition having elementalmetal atoms contained within the cross-linked dendritic polymer network,whereby the nanocomposite composition exhibits adequate surfaceelectrical conductivity for electroplating; and (e) electroplating ametal onto the nanocomposite composition to form an electricallyconductive deposit.

[0012] These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification and claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention provides methods of selectively depositinga metal on a dielectric substrate by forming a polymeric coating on thedielectric substrate, sorbing metal ions into the polymeric coating,reducing the sorbed metal ions to form a composite containing elementalmetal and exhibiting sufficient conductivity to allow electroplating ofa metal onto the composite composition, and electroplating a metal ontothe composite composition.

[0014] The polymer coating is prepared with a radially-layered dendriticcopolymer having a hydrophilic interior that is capable of sorbing metalions, and a hydrophobic exterior capable of adhering tenaciously to adielectric substrate. A radially-layered dendritic copolymer is adendritic copolymer having at least two chemically distinct domains, inwhich one of the domains surrounds the other domain, wherein thesolubility properties of the radially-layered dendritic polymer aredetermined by the chemical properties of the external domain. Morespecifically, the radially-layered dendritic polymers employed in theprocesses of this invention have a hydrophilic internal domain that iscapable of complexing or otherwise retaining metal cations, and ahydrophobic, water-insoluble external domain that surrounds hehydrophilic interior domain.

[0015] Examples of radially-layered dendritic copolymers that may beemployed in the processes of this invention are described in U.S. Pat.Nos. 5,739,218; 5,902,863; 5,938,934; and 6,077,500, each of which isincorporated in its entirety by reference herein. Preferredradially-layered dendritic copolymers for use in the processes of thisinvention include the radially-layered copoly(amidoamine-organosilicon)(PAMAMOS) and radially-layered copoly(propyleneimine-organosilicon)(PPIOS) dendrimers described in U.S. Pat. No. 5,739,218. Theseradially-layered copolymer dendrimers are prepared by reacting ahydrophilic dendrimer such as a poly(amidoamine) (PAMAM) orpoly(propyleneimine) (PPI) with an organosilicon modifier. In the caseof amine-terminated PAMAM and PPI dendrimers, the —NH₂ groups at thesurface of the dendrimer may be reacted with a silane or siloxane of therespective formulae XSiR_(n)Y_((3-n)) or XR^(n) _(p)Y_(2-p)Si(OSiR^(n)₂)_(m)OSiR^(n) _(n)Y_(3-n) wherein m represents zero to 100; nrepresents zero, one, two, or three; and p represents zero, one, or two.X can be any group that reacts with —NH₂ such as CH₂=═CHCOO(CH₂)₃—,ClCH₂—, BrCH₂— or ICH₂—. Other groups that react with —NH₂ can also beemployed, such as epoxy, ClCO(CH₂)_(a)—, R′″OCO(CH₂)_(a)—, NCO—R″″—, orNCOCH₂CH═CH—, wherein a in these other groups represents an integerhaving a value of 1-6, R, R′, R″, R′″, and R″″ are preferably alkylradicals containing 1-6 carbon atoms, most preferably methyl, an arylradical such as phenyl, or a fluoroalkyl radical such as —(CH₂)₂CF₃ or—(CH₂)₂(CF₂)₃CF₃. Y represents a group that does not react with —NH₂such as the vinyl group CH₂═CH—, the allyl group CH₂═CH—CH₂—, —OR,hydrogen, a triorganosiloxy radical, or a ferrocenyl radical.

[0016] Representative examples of such organosilicon compounds that canbe used herein, are (3-acryloxypropyl)methyldimethoxysilane,(3-acryloxypropyl)bis(vinyldimethylsiloxy) methylsilane,(3-acryloxypropyl)dimethyhnethoxysilane,(3-acryloxypropyl)trimethoxysilane, chloromethyldimethylvinylsilane,iodomethyldimethylvinylsilane, chloromethyldimethylallylsilane, etc.

[0017] Lower generation hydrophilic dendrimers (e.g., generation 2, 3 or4) are preferred starting materials for preparation of theradially-layered copolymeric dendrimers used in the process of thisinvention on account of their lower cost as compared with highergeneration dendrimers. Desirably, the reaction between the surfacefunctional groups of the hydrophilic dendrimer and the organosiliconmodifier is sufficient to render the reaction product waterinsoluble.

[0018] Other dendritic polymers that can be reacted with anorganosilicon modifier to produce a radially-layered dendritic copolymerhaving a hydrophilic interior capable of sorbing (i.e., complexing withor otherwise retaining) metal cations and a hydrophobic exterior capableof being cross-linked and capable of adhering tenaciously to adielectric (i.e., electrically nonconductive) substrate includehyperbranched polymers such as hyperbranched poly(propyleneimines),poly(amidoamines), polyamides, etc.

[0019] As is the case will all dendritic polymers (including dendrimers,dendrons, hypercombbranched polymers and the like), hyperbranchedpolymers are polymers having branches upon branches. However, incontrast to dendrimers, hyperbranched polymers can be prepared in aone-step, one-pot procedure. This facilitates the synthesis of largequantities of materials at high yields and at a relatively low cost. Ahyperbranched polymer contains a mixture of linear and branchedrepeating units, whereas an ideal dendrimer contains only branchedrepeating units without any linear repeating units. The degree ofbranching, which reflects the fraction of branching sites relative toperfectly branching system (i.e., an ideal dendrimer), for ahyperbranched polymer is greater than 0 and less than 1, with typicalvalues being from about 0.25 to about 0.45 (about 25% to about 45%).Unlike ideal dendrimers which have a polydispersity that approaches 1,hyperbranched polymers have a polydispersity that increases withincreasing molecular weight, with typical polydispersities being greaterthan 1.1 even at a relatively low weight average molecular weight suchas 1000 Daltons, and with polydispersities greater than 1.5 beingtypical for hyperbranched polymers having a weight average molecularweight of about 10,000 or higher. These differences between thepolydispersities and degree of branching of hyperbranched polymersversus dendrimers are indicative of the relatively higher non-ideality,randomness, and irregularity of hyperbranched polymers as compared withdendrimers. However, as with the PAMAM and PPI dendrimers, hydrophilichyperbranched polymers such as hyperbranched polypropylamine are capableof sorbing metal cations and retaining elemental metal after reductionof the metal cations in situ. In addition, surface groups on thehyperbranched polymers can be reacted with organosilicon modifiers toprovide radially-layered dendritic polymers suitable for use in theprocesses of this invention.

[0020] Hyperbranched polymers that are suitable for use in thisinvention will typically have a degree of branching of from about 20% toabout 55%, and more typically from about 25% to about 45%, and a weightaverage molecular weight of from about 1000 to about 25,000, moretypically from about 2000 to about 20,000, and most typically from about2000 to about 10,000.

[0021] The dendritic polymer precursors that may be used for preparingthe radially-layered dendritic copolymers used in the processes of thisinvention include generally any hydrophilic dendritic polymer (e.g.,hyperbranched polymer, dendrimer, etc.) having terminal functionalgroups that can be reacted with organosilicon modifiers that are capableof providing a reaction product having a cross-linkable hydrophobicsurface, and which are capable of sorbing metal cations and retainingelemental metal after reduction of the metal cations in situ.

[0022] The processes of this invention may be employed in a variety ofapplications in which metallization (i.e., deposition of a metalliclayer) on a dielectric (i.e., electrically nonconductive) surface isdesired. For example, the process of this invention may be used in avariety of applications in which conventional electroless metaldeposition is used to provide sufficient surface electrical conductivityto permit metal plating on a dielectric substrate. Commerciallyimportant applications include additive processes for forming fine-lineelectrical circuit patterns on rigid or flexible electrically insulative(dielectric) substrates to produce printed circuits, printed wiringboards, and the like.

[0023] Typical dielectric substrates usually have a thickness of fromabout 14 to about 40 mils, and more typically from about 2 to about 25mils. The dielectric substrate are typically thermoset or thermoplasticresins and can be reinforced with glass fiber or may contain fillers.Typical thermosetting polymeric materials used for forming thedielectric substrate include epoxy resins, phenolic based materials andpolyamides. Flexible circuits are typically fabricated from polyimide orpolyester films which are only 1 to 2 mils thick. Examples of somephenolic-type materials include copolymers of phenol, resorcinol andcresol. Examples of suitable thermoplastic materials that may be usedfor forming a dielectric substrate include polyolefins such aspolypropylene, polysulfones, polycarbonates, nitrile rubbers, ABSpolymers and fluorinated polymeric materials such aspolytetrafluoroethylene. A suitable dielectric substrate that is widelyused commercially for preparing printed wiring boards is aglass-reinforced epoxy substrate designated as FR-4.

[0024] Another important application of this invention is metallizationof the walls of through-holes drilled through a dielectric substrate toprovide an electrically conductive pathway from one side of thedielectric substrate to the other.

[0025] The radially-layered dendritic polymers may be applied to asubstrate surface or to selected areas of a substrate surface in theform of a coating composition. Suitable coating compositions comprise asolvent capable of solubilizing the selected radially-layered dendriticpolymer, the selected radially-layered dendritic polymer, and mayoptionally contain fillers or other agents for adjusting the rheology ofthe coating composition for a selected coating technique. Suitablesolvents for the coating compositions used in the processes of thisinvention include lower molecular weight alcohols, such as methanol,ethanol, propyl alcohol, diethylene glycol, and combinations thereof.Suitable concentrations of the radially-layered dendritic polymer in thecoating compositions are typically from about 10% to about 30%, and moretypically from about 15% to 25%, by weight of the composition. Examplesof suitable rheological agents include fillers such as fumed silica,calcium carbonate and talc. Examples of suitable additives to adjustproperties of the resulting coatings include co-reagents, such astetraethoxysilane or alpha,omega-telechelic linear polymers, side-chainfunctionalized polymers, fillers, antioxidants, etc.

[0026] A variety of techniques may be employed for applying the coatingcomposition to a substrate. Examples include roller-coating,dip-coating, spray-coating, and highly selective direct printingtechniques using a plotter pen, transfer printing, rubber-stampingand/or inkjet printing. The thickness of the coating is not especiallycritical. However, the minimum coating thickness needed to achieve adesired electrical surface conductivity for electroplating subsequent tocuring of the coating, sorption of metal cations, and reduction of themetal cations to elemental metal is desired to minimize cost. Suitablethicknesses for a dried coating (after evaporation of the solvent) aretypically from about 5 micrometers to about 25 micrometers. Althoughthicker coatings may be used, this would likely increase the cost of theprocess without adding any significant benefit.

[0027] The radially-layered dendritic polymers used in the processes ofthis invention have reactive silicon-functional groups at their outersurface. The reactive silicon-functional groups at the outer surfaceinclude moieties having the formula: R_(3-z-y)W_(y)Si, where X and Wrepresent reactive groups; z is 1, 2 or 3; and y is 0, 1, or 2. Forpurposes of the present invention, any reactive silicon-functional groupX or W can be used, including for example, —R′—NH₂, —R′—NR₂, mercapto(—R′SH), vinyl (—HC═CH₂), allyl, hydrogen, halogen, acetoxy (—O(O)CCH₃),ureido, acryloyl, and alkoxy or aryloxy (—OR). R represents an alkylgroup containing 1-6 carbon atoms, or an aryl group such as phenyl; andR′ represents the corresponding alkylene or arylene groups. The alkoxygroup —OR is the most preferred reactive group. In addition, W can alsobe a non-reactive group, in which case it is preferably different from—CH₃ or —X.

[0028] Cross-linking of the radially-layered dendritic polymers to formcross-linked dendritic polymer networks can be achieved by any number ofdifferent types of reactions, including the following:

[0029] (1) catalyzed addition reactions such as hydrosilation or thioladdition, in the case of ≡SiCH═CH₂, ≡Si—CH₂—CH═CH₂, ≡Si—R—SH, or ≡SiHsurface functionalized dendrimers;

[0030] (2) self-catalyzed reactions such as hydrolysis with moisture orwater, in the case of ≡SiCl and ≡Si—OR surface functionalizeddendrimers;

[0031] (3) non-catalyzed addition reactions such as Michael addition inthe case of acryloyl groups; and

[0032] (4) condensation reactions.

[0033] The cross-linking may be performed with or without one or moreadded reactants, such as small molecular weight or oligomeric (i)difunctional reagents A₂, (ii) trifunctional reagents A₃, (iii)polyfunctional reagents A_(x) where x is 4 or more, or (iv) by simplyusing moisture from the atmosphere, or intentionally added water.Representative A₂, A₃, and A_(x) reagents include organohalosilanes,tetrahalosilanes, organosilanols, organooxysilanes such asdialkoxysilanes, trialkoxysilanes, and tetraalkoxysilanes,aminoalkylalkoxysilanes, haloalkylalkoxysilanes, organo-H-silanes,organoaminosilanes, organoacyloxysilanes such as acetoxysilanes,organosilsesquioxanes, ureido-substituted silanes, vinyl-substitutedsilanes, allyl-substituted silanes, etc. Corresponding organic ororganometallic compounds can also be employed.

[0034] It is known that dendritic polymers can degrade at elevatedtemperatures. For example, PAMAM dendrimers begin to lose their abilityto form nanocomposites (i.e., sorb and retain metal cations) due to aretro-Michael reaction. The rate of this reaction is dependent ontemperature, but it is known to occur within hours at temperatures ofabout 120° C. and above. Accordingly, it is preferred that the curing orcross-linking of the radially-layered dendritic polymer coating beperformed at a temperature, or within a temperature range, that issufficiently high to accelerate the curing process, but sufficiently lowto prevent excessive degradation of the radially-layered dendriticpolymer. Further, it has been determined that the extent of cure isinversely related to the ability of the cured coating to sorb metalcations, i.e., higher degrees of cross-linking reduce the rate of metalcation sorption and the quantity of metal cation that may be sorbed intothe cross-linked dendritic polymer network. Accordingly, it may bedesirable to cure the coating in two stages, including a first stage toprovide adequate mechanical properties and adhesion to the substrateprior to sorption of the metal cations, and a second stage cure aftersorption of the metal cations to provide sufficient mechanicalproperties and adhesion to the substrate for subsequent reduction of themetal cations and electroplating of a metal on to the cross-linkeddendritic polymer network. The optimum curing process (including thenumber of cure stages, cure temperatures and cure times, etc.) willdepend on a variety of factors relating to the type of radially-layereddendritic polymer that is used. In the case of a radially-layeredPAMAMOS dendrimer that is the product of a generation 3 PAMAM dendrimerand (3-acryloxypropyl)methyldimethoxysiliane, a suitable cure processinvolves a first curing stage conducted at a temperature of about 100°C. for 24 hours, followed by sorption of a metal cation, and then asecond stage cure at 100° C. for an additional 24 hours. Suitable andoptimum curing processes can be determined by routine experimentationfor various radially-layered dendritic polymers.

[0035] It is believed that with the exception of Group I elements, allmetal cations can be sorbed by radially-layered dendritic polymers suchas PAMAMOS and/or PPIOS dendrimers. Representative metal cations thatmay be sorbed into the radially-layered dendritic polymers include Cu⁻¹,Cu⁺², Fe⁺², Fe⁺³, Au⁺³ Co⁺², Ag⁺¹, Pd⁺², Rh⁺³, Ni⁺², Pt⁺², Pt⁺⁴, Eu⁺³Tb⁺³ and Cd⁺². The metal cations may be placed in solution with anysuitable anion such as acetate, chloride or sulfate anions, with apreferred metal cation being Cu⁺² on account of its excellent electricalconductivity and relatively low cost.

[0036] After cross-linking of the radially-layered dendritic copolymerand sorption of the metal cations in the cross-linked dendritic polymernetwork, the metal cations in the cross-linked dendritic polymer networkare reduced to form a nanocomposite composition having elemental metalatoms contained or encapsulated within the cross-linked dendriticpolymer network, whereby the nanocomposite composition exhibits adequatesurface electrical conductivity for a subsequent electroplating step.Several choices of chemical reducing agents are available for this task.Sodium borohydride, hydrazine, ascorbic acid, alcohols, and sodiumcitrate are examples of chemical reducing agents that have beensuccessfully used for reduction of metal cations sorbed in a dendriticpolymer to form elemental metal nanoclusters (i.e., clusters ofelemental metal atoms having nanoscopic dimensions in the range from 1nanometer to 10 nanometers). In the case of copper nanocomposites ofPAMAM dendrimers, clusters residing inside the dendrimer have a meansize of less than about 1.8 nanometers, while copper particles thatagglomerated outside of the dendrimer were determined to beapproximately 9 nanometers in diameter. Reduction of the sorbed metalcations can be achieved by adding a several-fold excess of solid sodiumborohydride (or other reducing agent) in an aqueous solution andcontacting the solution with the cross-linked coating compositioncontaining sorbed metal cations, such as by immersion of the coatedsubstrate in the solution. Reduction of the copper cations sorbed in aradially-layered PAMAMOS dendrimer network can be achieved within about20 minutes at room temperature by immersing the coated substrate in asodium borohydride-water solution having a BH₄ ⁻ concentration of fromabout 1 to about 2 grams per 100 milliliters. However, other reducingagents may be used in an amount effective to achieve sufficientreduction of the sorbed metal cations to achieve sufficient surfaceelectrical conductivity to facilitate a subsequent electroplatingoperation.

[0037] After the metal cations in the cross-linked dendritic polymernetwork have been reduced to provide adequate surface electricalconductivity for electroplating and any optional second stage curing hasbeen achieved, a metal is electroplated onto the nanocompositecomposition to form an electrically conductive deposit. Nanocompositefilms formed by depositing a radially-layered PAMAMOS dendrimer on asubstrate, cross-linking the deposited PAMAMOS film, sorbing Cu⁺²cations into the resulting cross-linked dendritic polymer network andreducing the metal cations to form elemental metal atoms encapsulatedwithin the cross-linked dendritic polymer network have been shown toproduce nanocomposite compositions exhibiting a surface resistivity offrom about 10⁻⁵ to about 10⁻⁷ ohms per square centimeter, which issufficient for conventional direct electroplating processes.

[0038] There are three different commercial electroplating bath types:sulfuric acid baths, cyanide baths, and copper pyrophosphate baths. Anyof the conventional electroplating baths may be used. However, cyanidebaths are rarely used because of toxicity and waste problems, and it hasbeen found that acid baths can adversely affect coating adhesion and cancause delamination and/or disintegration of the nanocomposite film.Accordingly, copper pyrophosphate baths are preferred. Excellent platingresults without any disintegration and/or delamination of thenanocomposite composition have been achieved using a commerciallyavailable electroplating bath comprising 10 weight percent copperpyrophosphate.

[0039] Although preferred applications for the processes of thisinvention include metallization of through-holes or vias in printedwiring boards, and formation of electrically conductive circuit patternsfor the electronics industry, the processes of this invention can beused for depositing a decorative metal electroplate on plastic(thermoset or thermoplastic) substrates used, for example, as housingsfor electronic devices such as computers, personal digital assistants(PDAs), cellular telephones, audio and/or video recording devices, etc.Decorative applications may include metallization of all exposedsurfaces of a substrate or selected surfaces thereof and also mayinclude decorative metallized patterns. An advantage of the inventionfor both decorative and functional applications is that it eliminatesproblems associated with electroless plating of a metal on a dielectricsubstrate.

[0040] Patterning of the radially-layered dendritic copolymer coating orcross-linked dendritic polymer network can be achieved during depositionof the radially-layered dendritic copolymer onto the surface of thesubstrate using direct printing techniques which involve application ofa coating composition containing the radially-layered dendriticcopolymer to selected surfaces of the substrate in the desired pattern.Direct printing of a desired electrically conductive circuit pattern ordecorative pattern can be achieved by using, for example, a plotter pen,transfer printing, rubber-stamping, or inkjet printing. The desiredprinted pattern can be cross-linked, contacted with a solutioncontaining metal cations to sorb the metal cations into the crosslinkeddendritic polymer network, contacted with a reducing agent to reduce themetal cations in the cross-linked dendritic polymer network to form ananacomposite composition having elemental metal atoms encapsulatedwithin the cross-linked dendritic polymer network, and electroplatedwith a metal to form an electrically conductive circuit pattern ordecorative pattern corresponding with the printed pattern of theradially-layered dendritic copolymer. This direct printing processallows a fine-line conductive metal pattern to be formed on a dielectricsubstrate without the use of etching techniques, photolithographictechniques, masks, mask alignment, electroless deposition, and thevariety of problems associated therewith.

[0041] As an alternative, the desired pattern can be formed by firstdepositing a coating composition containing the radially-layereddendritic copolymer onto a substrate, cross-linking the radially-layereddendritic copolymer to form a dendritic polymer network, and selectivelysorbing the metal cations in the cross-linked dendritic polymer networkin a pattern corresponding with a desired electrically conductivecircuit pattern or a desired decorative metal pattern. This can beachieved by masking those portions of the coating where metallization isnot desired, and subsequently contacting the areas of the dendriticpolymer network that are exposed through the mask with a solutioncontaining metal cations. Because sorption of metal cations into thedendritic polymer network occurs substantially in only one direction(from the surface to the substrate) with very little lateral diffusionof the metal cations through the dendritic polymer network, sorption ofthe metal cations occurs only in the unmasked areas, such that, uponsubsequent reduction of the sorbed metal cations, a metal can beelectroplated on selected portions of the dendritic polymer network in aprecise pattern corresponding to the pattern defined by the mask. Thistechnique can be used for forming fine-line conductive metal circuitpatterns. A desired mask pattern may be applied to the cross-linkedradially-layered dendritic copolymer coating using techniques such asroller coating, plotter pen, transfer printing, rubber-stamping andinkjet printing. The coating composition used to apply the mask shouldbe of a thickness and type that has the ability to effectively blockabsorption of the metal cation into the cross-linked dendritic polymernetwork and should be easily removable from the cross-linkedradially-layered dendritic copolymer coating, such as with a strippersolvent, after sorption of the metal cations into the cross-linkeddendritic polymer network and before electroplating of a metal onto thenanocomposite composition.

[0042] As another alternative, a desired electrically conductive circuitpattern or decorative pattern can be formed with the process of thisinvention using a variety of etching techniques. A first approach isbased on etching or scribing a desired circuit pattern or decorativepattern in the dielectric substrate, filling only the resulting trencheswith a radially-layered dendritic copolymer having a hydrophilicinterior and an organosilicon exterior, cross-linking theradially-layered dendritic copolymer to form a dendritic polymernetwork, sorbing metal cations in the cross-linked dendritic polymernetwork, reducing the metal cations in the cross-linked dendriticpolymer network, and electroplating a metal onto the resultingnanocomposite composition to form an electrically conductive circuitpattern or decorative pattern.

[0043] Filling of only the trenches etched in a susbstrate can beachieved by applying a coating composition containing theradially-layered dendritic copolymer to the surface of the etched orscribed substrate and removing excess coating composition from thesurface such as with a squeegee. Smooth wall trenches suitable forcreating fine-line circuit patterns can be achieved with a laser or witha plasma and a mask.

[0044] Another etching technique that can be used involves first coatingthe entire substrate surface with a coating composition containing aradially-layered dendritic copolymer having a hydrophilic interior andan organosilicon exterior, curing the radially-layered dendriticcopolymer, then ablatively removing the cross-linked radially-layereddendritic copolymer from the dielectric substrate wherever circuitry (ordecorative metallization) is not desired. The resulting patternedcross-linked radially-layered dendritic copolymer may then be contactedwith a solution containing metal cations to cause sorption of the metalcations in the cross-linked dendritic polymer network. Thereafter, themetal cation in the cross-linked dendritic polymer network may bereduced to form a patterned nanocomposite composition that exhibitsadequate surface electrical conductivity for electroplating, and a metalmay be electroplated onto the nanocomposite composition to form adesired electrically conductive circuit pattern or decorative pattern.

[0045] A third etching technique for forming a desired electricallyconductive circuit pattern or decorative metal pattern involvesapplication of a mask over the entire surface of a cross-linkedradially-layered dendritic copolymer coating applied to a surface of adielectric substrate. A trench pattern is then formed in the mask. Thetrench pattern may be formed mechanically, with a laser, with reactiveion etching (RIE), or by plasma ablation. The trench pattern is formedto a sufficient depth through the mask to expose the underlyingcross-linked radially-layered dendritic copolymer. The exposed patternmay be contacted with a solution containing metal cations to allowpenetration and sorption of the metal cations into the cross-linkeddendritic polymer network. Thereafter, the sorbed metal cations may bereduced, and a metal may be electroplated onto the portions of thedendritic polymer network containing elemental metal atoms to form adesired electrically conductive circuit pattern or decorative metalpattern. An advantage of this process is the ability to anchor thecircuit pattern with a slug of copper anchored to the walls of thetrench pattern, and the ability of opening via holes for through-holeplating in a single step. The radially-layered dendritic copolymer canbe coated onto the dielectric substrate using a spin-coating process.The portions of the dendritic polymer network surrounding the metalcircuit pattern could potentially become a low conductivity dielectricbecause, during thermal annealing of each conducting integrated circuitlayer, the dendritic polymer units comprising the dendritic polymernetwork would likely act as porogens, selectively decomposing fromwithin the dendritic polymer network to form a closed cell foam having alow conductivity.

[0046] Another important commercial application for the processes ofthis invention is direct plating of through-holes. Through-hole platingis used to provide an electrically conductive path from one side orsurface of a double-sided board to the opposite side. Because the centerof each board layer is a dielectric material (typically a combination ofwoven glass and epoxy resin) and will not conduct electrical current, amethod of forming a conductive layer over the dielectric core isnecessary. The predominant method of accomplishing this has been byelectroless copper plating. The major steps in the electroless platingof printed wiring board through-holes are cleaning, activation,acceleration and copper deposition. While none of the chemistriespresent in the electroless plating line are particularly expensive(except for palladium catalyst), the typical process line is long, withas many as 17 processing tanks and 8 discrete steps. Additionally, asdrilled holes become smaller and multi-layer boards become thicker(higher aspect ratio) with more layers, electroless copper will oftennot plate all surfaces, leaving voids or no connection at all, thuscreating open circuits.

[0047] Although electroless plating has produced reliable interconnectsfor decades, new limits on worker exposure to formaldehyde anddifficulties in removing chelated copper from the waste stream havecaused printed wiring board shops to seek alternatives. Alternativeshave been developed which eliminate the use of formaldehyde andchelating agents, as well as providing simplified processes by usingactivated graphic or carbon colloidal solutions, or a heavy applicationof a palladium activator. However, despite the commercial availabilityof these processes, electroless copper deposition is used morefrequently than other processes.

[0048] The present invention offers a revolutionary process that coatsthe entire through-hole wall with a smooth layer of conductive elastomerwhich may be directly and efficiently electroplated using conventionalelectroplating techniques. Very little radially-layered dendriticcopolymer is required. Aqueous copper salt and borohydride baths couldbe replenished continuously without creating waste streams, and theelastomeric property of the dendritic polymeric network would allowreduced stresses within the via hole during thermal cycling. The processinvolves depositing a radially-layered dendritic copolymer on thethrough-hole surface, cross-linking the radially-layered dendriticcopolymer, sorbing metal cations into the cross-linked dendriticpolymer, reducing the metal cations in the cross-linked dendriticpolymer, and electroplating a metal onto the resulting nanocompositecomposition to form an electrically conductive pathway from one side ofa circuit board to the other side.

[0049] The organosilicon modified dendritic polymer coatings of thisinvention are generally elastomeric and adhere tenaciously to manydielectric surfaces such as organic polymer films, silica, glassceramics, silicon wafers, and plastics. The nanocomposite coatings ofthis invention offer a new and practical method of advancing technologywhile reducing the cost of next generation printed circuit interconnectsfor microelectronics applications. The unique chemistry of theradially-layered dendritic copolymer nanocomposites allows, for thefirst time, an easily prepared, relatively inexpensive, conducting metalsurface in a mechanically viable polymeric coating. The processes ofthis invention are expected to fundamentally alter the way in whichprinted wiring boards are manufactured. This technology is capable ofproviding increased interconnect capacity because of the elimination oftroublesome steps in the printed wiring board fabrication sequence and,at the same time, reduced costs by simplifying a complex multi-stepprocess. It is believed that the process of this invention couldpotentially replace current printed wiring board fabrication processesinvolving etching of a copper layer laminated to a substrate(subtractive process) as well as additive processes involvingelectroless plating.

EXAMPLES Example 1 Preparation of Radially-Layered PAMAMOS CopolymericDendrimer

[0050] A radially-layered PAMAMOS copolymeric dendrimer was prepared bymodification of a generation 3 ethylene diamine (EDA)-core PAMAMdendrimer with (3-acryloxypropyl)dimethoxymethyl-silane.

[0051] All glassware used in this example was first dried overnight in aheating oven and then assembled while still hot. A three-necked roundbottomed reaction flask was equipped with a nitrogen inlet, a stopper,and a condenser with another stopper at its top, evacuated to a partialvacuum, and flame-dried using several nitrogen-vacuum purging cycles.After the assembled glassware was cooled to room temperature, i.e.,20°-25° C., the apparatus was filled with nitrogen predried by passingit over drierite, and the stopper on the flask was removed under astrong counter-stream of dry-nitrogen and replaced by a rubber septum. Arubber balloon was placed on the top of the condenser in order to allowcontrol of slight overpressures in the assembly. The syringes were alsodried overnight in the oven and kept in a desiccator until used. Thedendrimer was lyophilized under high vacuum overnight in around-bottomed flask, then weighed (1.56 g; 0.23 mmol; 14.45 mmol of —NHgroups), placed under dry nitrogen, and the flask was equipped with arubber septum. Anhydrous methanol (10 ml) was added via syringe throughthe septum. When the dendrimer was dissolved, the mixture wastransferred with a syringe to the apparatus.(3-Acryloxypropyl)dimethoxymethylsilane (A; 4.2 ml; 4.2 g; 17.79 mmol)was added, and the mixture was left at room temperature, with stirring,under nitrogen atmosphere for 24 hours. Methanol was evaporated firstunder a stream of dry nitrogen, then under vacuum. The percentmodification of the dendrimer was determined by ¹H Nuclear MagneticResonance (NMR): 60% of (A) had reacted, so 74% of the —NH groups hadbeen modified. The modified dendrimer was stable as long as it was keptin an anhydrous solution. Its characterization by ¹H NMR in deuteratedchloroform (CDCl₃) gave: 0.02 ppm (s; ≡Si—CH₃); 0.52 ppm (m; —CH₂—Si≡);1.61 ppm (m; —COO—CH₂—CH₂CH₂—Si≡); 2.4-3.6 ppm (PAMAM interior protons);3.94 ppm (t; PAMAM-COO—CH₂—); 4.02 ppm (t, CH₂═CH—COO—CH₂—); 5.68-6.32ppm (d+d×d+d; CH₂═CH—COO—). ¹³CNMR in CDCl₃, gave: −6.18 ppm (≡Si—CH₃);8.89 ppm (—CH₂—Si≡); 21.82 ppm (—COO—CH₂ 13 CH₂—CH₂—Si≡); 32.37 ppm(═N—CH₂—CH₂—COO—(CH₂)₃—Si—); 33.54 ppm (—CH₂—CO—NH—); 34.7 ppm(—NH—CH₂—CH₂—COO—(CH₂)₃—Si≡); 37.10 and 37.29 ppm (—CO—NH—CH₂—); 38.76ppm (—CO—NH—C—CH₂—NH—(CH₂)₂—COO—); 44.43 ppm(—CO—NH—CH₂—CH₂—NH—(CH₂)₂—COO—); 48.37 ppm (—NH—CH₂—CH₂—COO—(CH₂)₃—Si≡); 48.92 ppm (—CO—NH—CH₂—CH₂—N—((CH₂)₂—COO—)₂); 49.54 ppm(—CO—NH—CH₂—CH₂—N═); 49.89 ppm (≡Si—O—CH₃); 51.33 ppm (═N—CH₂—CH₂—COO—);52.20 and 52.60 ppm (═N—CH₂—CH₂—CONH); 66.31 ppm (═N—(CH₂)₂—COO—CH₂—);128.32 and 130.18 ppm (CH₂═CH—); 172.21 and 172.31 ppm (—CH₂—CH₂—COO—and —CO—NH—) and the unreacted acrylate reagent at: —6.18 ppm (≡Si—CH₃);8.89 ppm (—CH₂—Si≡); 21.82 ppm (—COO—CH₂—CH₂—CH₂—Si—); 49.89 ppm(≡Si—O—CH₃); 66.36 ppm (CH₂ CH—COO—CH—); 128.32 and 130.18 ppm(CH₂═CH—); 165.92 ppm (CH₂═CH—COO—).

Example 2 Preparation of PAMAMOS Dendrimer Coating on a MicroelectronicSubstrate

[0052] A 20 weight percent solution of the PAMAMOS dendrimer of Example1 was coated onto a FR-4 glass-epoxy substrate and cured for 5 days at60° C. to form an elastomeric coating over the substrate.

Example 3 Sorption of Copper Ions and Reduction Thereof in the PAMAMOSDendrimer Coating

[0053] Copper ions were sorbed into the coating of Example 2 byimmersing the coated substrate for 2 hours in an aqueous solution ofcopper acetate having a concentration of 0.1 M. The coating appearedblue from the absorbed copper salt. Thereafter, the coated substrate wasdried and cured for 22 hours at 100° C. After the second curing stage,the copper ions sorbed in the PAMAMOS dendrimer network were reduced toelemental metal by immersing the coated substrate in an aqueous solutionof sodium borohydride having a concentration of about 2.0 grams per 100milliliters. The coating turned from blue to a shiny metallic coppercolor as the Ca⁺² ions were reduced to Cu⁰.

Example 4 Electroplating of Nanocomposite Composition

[0054] The resulting nanocomposite composition of Example 3 havingelemental metal atoms encapsulated within a cross-linked PAMAMOSdendrimer network have a surface resistivity of between 10⁻⁵ to 10⁻⁷ohms per square centimeter, which was sufficient for directelectroplating using a commercially available copper pyrophosphate bathhaving a copper pyrophosphate concentration of about 10 weight percent.

[0055] The above description is considered that of the preferredembodiments only. Modifications of the invention will occur to thoseskilled in the art and to those who make or use the invention.Therefore, it is understood that the embodiments described above aremerely for illustrative purposes and not intended to limit the scope ofthe invention, which is defined by the following claims as interpretedaccording to the principles of patent law, including the doctrine ofequivalents.

The invention claimed is:
 1. A process for depositing an electricallyconductive material on a selected surface of a dielectric substrate,comprising: depositing on a selected surface of a dielectric substrate aradially-layered dendritic copolymer having a hydrophilic interior and ahydrophobic exterior; cross-linking the radially-layered dendriticcopolymer to form a dendritic polymer network; sorbing metal cationsinto the cross-linked dendritic polymer network; reducing the metalcations in the cross-linked dendritic polymer network to form ananocomposite composition having elemental metal atoms contained in thecross-linked dendritic polymer network, whereby the nanocompositecomposition exhibits adequate surface electrical conductivity forelectroplating; and electroplating a metal onto the nanocompositecomposition to form an electrically conductive deposit.
 2. The processof claim 1, wherein the hydrophobic exterior of the radially-layereddendritic polymer has an organosilicon composition.
 3. The process ofclaim 1, wherein the radially-layered dendritic copolymer is the productof a hydrophilic dendritic polymer and an organosilicon modifier.
 4. Theprocess of claim 1, wherein the radially-layered dendritic copolymer isa PAMAMOS dendrimer having a hydrophilic PAMAM interior and anorganosilicon exterior.
 5. The process of claim 1, wherein theradially-layered dendritic copolymer is a PPIOS dendrimer having ahydrophilic PPI interior and an organosilicon exterior.
 6. The processof claim 1, wherein the radially-layered dendritic copolymer is ahyperbranched polymer.
 7. The process of claim 1, wherein theradially-layered dendritic copolymer is a hyperbranched polymer having ahydrophilic poly(propyleneimine) interior and an organosilicon exterior.8. The process of claim 1, wherein the radially-layered dendriticcopolymer is a hyperbranched polymer having a hydrophilicpoly(amidoamine) interior and an organosilicon exterior.
 9. The processof claim 1, wherein the radially-layered dendritic copolymer is ahyperbranched polymer having a hydrophilic interior and a hydrophobicexterior.
 10. The process of claim 1, wherein the radially-layereddendritic copolymer is a hyperbranched polymer having a hydrophilicpolyamide interior and an organosilicon exterior.
 11. The process ofclaim 1, wherein the radially-layered dendritic copolymer is the productof a hydrophilic dendritic polymer and an organosilicon modifier havingthe formula: XSiR_(n)Y_((3-n)) orXR″_(p)Y_(2-p)Si(OSiR″₂)_(m)OSiR″_(n)Y_(3-n) wherein m represents zeroto 100; n represents zero, one, two, or three; and p represents zero,one, or two; X can be any group that reacts with —NH₂; and Y representsa group that does not react with —NH₂.
 12. The process of claim 11,wherein X is selected from CH₂═CHCOO(CH₂)₃—, ClCH₂—, BrCH₂—, ICH₂—,epoxy, ClCO(CH₂)_(a)—, R′″OCO(CH₂)_(a)—, NCO—R″″—, and NCOCH₂CH═CH—,wherein a in these other groups represents an integer having a value of1-6, R, R′, R″, R′″, and R″″ are alkyl radicals containing 1-6 carbonatoms or a fluoroalkyl radical containing 1-6 carbon atoms.
 13. Theprocess of claim 11, wherein Y is selected from vinyl, allyl, —OR,hydrogen, a triorganosiloxy radical, and a ferrocenyl radical.
 14. Theprocess of claim 3, wherein the organosilicon modifier is selected fromthe group consisting of (3-acryloxypropyl)methyldimethoxysilane,(3-acryloxypropyl)bis(vinyldimethylsiloxy) methylsilane,(3-acryloxypropyl)dimethylmethoxysilane,(3-acryloxypropyl)trimethoxysilane, and chloromethyldimethylvinylsilane,iodomethyldimethylvinylsilane, and chloromethyldimethylallylsilane, etc.15. The process of claim 1, wherein the radially-layered dendriticcopolymer is the product of a PAMAM dendrimer and an organosiliconmodifier represented by the formula: XSiR_(n)Y_(3-n)) orXR″_(p)Y_(2-p)Si(OSiR″₂)_(m)OSiR″_(n)Y_(3-n) wherein m represents zeroto 100; n represents zero, one, two, or three; and p represents zero,one, or two; X is selected from CH₂═CHCOO(CH₂)₃—, ClCH₂—, BrCH₂—, ICH₂—,epoxy, ClCO(CH₂)_(a)—, R′″OCO(CH₂)_(a)—, NCO—R″″—, and NCOCH₂CH═CH—,wherein a in these other groups represents an integer having avalue of 1-6, R, R′, R″, R′″, and R″″ are alkyl radicals containing 1-6carbon atoms or a fluoroalkyl radical containing 1-6 carbon atoms; and Yis selected from vinyl, allyl, —OR, hydrogen, a triorganosiloxy radical,and a ferrocenyl radical.
 16. The process of claim 15, wherein the PAMAMdendrimer is a generation 0, 1, 2, 3 or 4 dendrimer.
 17. The process ofclaim 1, wherein the radially-layered dendritic copolymer is the productof a PPI dendrimer and an organosilicon modifier represented by theformula: XSIR_(n)Y_((3-n)) orXR″_(p)Y_(2-p)Si(OSiR″₂)_(m)OSiR″_(n)Y_(3-n) wherein m represents zeroto 100; n represents zero, one, two, or three; and p represents zero,one, or two; X is selected from CH₂═CHCOO(CH₂)₃—, ClCH₂—, BrCH₂—, ICH₂—,epoxy, ClCO(CH₂)_(a)—, R′″OCO(CH₂)_(a)—, NCO—R″″—, and NCOCH₂CH═CH—,wherein a in these other groups represents an integer having a value of1-6, R, R′, R″, R′″, and R″″ are alkyl radicals containing 1-6 carbonatoms or a fluoroalkyl radical containing 1-6 carbon atoms; and Y isselected from vinyl, allyl, —OR, hydrogen, a triorganosiloxy radical,and a ferrocenyl radical.
 18. The process of claim 17, wherein the PPIdendrimer is a generation 1, 2, 3 or 4 dendrimer.
 19. The process ofclaim 1, wherein cross-linking is achieved by hydrolysis of ≡SiCl or≡Si—OR end-groups of the radially-layered dendritic copolymer.
 20. Theprocess of claim 1, wherein cross-linking is achieved by hydrosilationor thiol addition reaction.
 21. The process of claim 1, whereincross-linking is achieved by Michael addition reaction.
 22. The processof claim 1, wherein cross-linking is achieved by condensation reactions.23. The process of claim 1, wherein the metal cations sorbed into thecross-linked dendritic polymer network are Cu⁺² ions.
 24. The process ofclaim 23, wherein the Cu⁺² ions are sorbed into the dendritic polymernetwork by contacting the dendritic polymer network with a copperacetate or copper sulfate solution.
 25. The process of claim 23, whereinthe reduction of Cu⁺² ions is achieved by contacting the dendriticpolymer network containing sorbed Cu+2 ions with a sodium borohydridesolution.
 26. The process of claim 1, wherein the electroplating isachieved in a copper pyrophosphate bath.
 27. The process of claim 1,wherein the selected surface of the dielectric substrate on which theradially-layered dendritic copolymer is deposited is a wall of athrough-hole in the dielectric substrate, whereby the electricallyconductive deposit forms an electrically conductive pathway from oneside of the substrate to another side of the substrate.
 28. The processof claim 1, wherein the electrically conductive material is deposited onselected surfaces of the dielectric substrate to form an electricalcircuit pattern.
 29. The process of claim 1, wherein deposition of theelectrically conductive material on the selected surfaces of thedielectric substrate is achieved by direct printing of a coatingcomposition containing the radially-layered dendritic copolymer to theselected surfaces of the substrate in a pattern that corresponds with adesired pattern of the electrically conductive deposit.
 30. The processof claim 29, wherein direct printing of the radially-layered dendriticcopolymer onto the selected surfaces of the substrate is achieved with aplotter pen, transfer printing, rubber-stamping or inkjet printing. 31.The process of claim 1, wherein depositing of the electricallyconductive material on the selected surfaces of the dielectric substrateis achieved by selectively sorbing the metal cations in the cross-linkeddendritic polymer network in a pattern corresponding with a desiredelectrically conductive deposit.
 32. The process of claim 1, whereinselective sorption of metal cations in a desired pattern is achieved bymasking portions of the cross-linked dendritic polymer network wheremetallization is not desired, and contacting areas exposed through themask with a solution containing metal cations.
 33. The process of claim1, wherein a desired pattern of electrically conductive material isdeposited on the dielectric substrate by etching or scribing the desiredpattern in the dielectric substrate prior to depositing theradially-layered dendritic copolymer on the dielectric substrate, theetching or scribing forming a trench pattern on the dielectricsubstrate, and depositing the radially-layered dendritic copolymer onlyin the trench pattern prior to crosslinking the radially-layereddendritic polymer.
 34. The process of claim 1, wherein a desired patternof electrically conductive material is deposited on the dielectricsubstrate by removing cross-linked radially-layered dendritic copolymerfrom the dielectric substrate wherever metallization is not desiredprior to electroplating the metal onto the nanocomposite composition.35. The process of claim 1, wherein a desired pattern of electricallyconductive material is deposited on the dielectric substrate byapplication of a mask over the cross-linked dendritic polymer network,formation of a trench pattern in the mask to a sufficient depth toexpose the underlying cross-linked radially-layered dendritic polymerprior to sorbing metal cations into the cross-linked dendritic polymernetwork, whereby the patterned mask allows sorption of metal cationsinto exposed areas of the dendritic polymer network and preventssorption of metal cations into the masked areas of the dendritic polymernetwork.
 36. The process of claim 1, wherein a desired pattern ofelectrically conducting material is deposited on the dielectricsubstrate by application of an ink mask over the copper nanocomposite ofthe cross-linked dendritic polymer network coating wherevermetallization is desired prior to electroplating and the coating is thenimmersed in an aqueous solution of ammonium persulfate whereby etchingunwanted copper nanocomposite, subsequent removal of the ink mask andsubsequent electroplating of the remaining circuit or decorativepattern.